Holden Astra: 1.6 turbo cracked rocker cover causing oil leak and rough running

The plastic rocker cover on the 1.6 turbo BK Astra cracks with age and heat, and because the cover also carries the crankcase breather the effect is more than a leak: unmetered air enters the engine, so the car idles roughly and can throw a misfire code as well as weeping oil. Owners in Australia report the repair in the region of A$700-1,300, which is high for what it is because the part is a full assembly rather than a gasket. Worth separating from an ordinary oil leak when you find one, because the symptoms overlap and the fix does not.

• Rough or hunting idle, sometimes with a misfire code
• Whistling or sucking noise from the top of the engine at idle
• Oil residue on or around the top of the engine
• Burning oil smell after a drive

1. 1

   Start the car and let it idle with the bonnet up, listening for a whistle or sucking noise from the top of the engine — that is the breather drawing air through a crack and is the giveaway that separates this from a plain oil leak.

2. 2

   Watch the tachometer for an idle that hunts up and down rather than sitting steady.

3. 3

   With a phone torch, look over the plastic rocker cover for hairline cracks, and along its edges for oil residue; look particularly around the breather area.

4. 4

   Smell for burning oil after the test drive.

5. 5

   Check the dash for an engine warning light, and ask whether one has ever appeared with a misfire.

6. 6

   If a workshop inspection is possible: have the fault memory read for misfire and fuel-trim codes, since a breather leak shows up clearly in long-term fuel trim.

Parts involved: Rocker / valve cover, Turbocharger.

$700 to $1,600 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has the rocker cover ever been replaced?”
• “Does the engine idle roughly or hunt when warm?”
• “Has an engine warning light ever appeared?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.